1. Characterization of the LacI-type transcriptional repressor RbsR controlling ribose transport in Corynebacterium glutamicum ATCC 13032.
- Author
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Nentwich SS, Brinkrolf K, Gaigalat L, Hüser AT, Rey DA, Mohrbach T, Marin K, Pühler A, Tauch A, and Kalinowski J
- Subjects
- ATP-Binding Cassette Transporters chemistry, ATP-Binding Cassette Transporters genetics, ATP-Binding Cassette Transporters metabolism, Amino Acid Sequence, Bacterial Proteins chemistry, Bacterial Proteins genetics, Base Sequence, Binding Sites, Biological Transport, Corynebacterium glutamicum genetics, DNA-Binding Proteins chemistry, DNA-Binding Proteins genetics, Gene Deletion, Molecular Sequence Data, Operon, Repressor Proteins chemistry, Repressor Proteins genetics, Bacterial Proteins metabolism, Corynebacterium glutamicum metabolism, DNA-Binding Proteins metabolism, Gene Expression Regulation, Bacterial, Repressor Proteins metabolism, Ribose metabolism
- Abstract
The gene products of the rbsRACBD (rbs) operon of C. glutamicum (cg1410-cg1414) encode a ribose-specific ATP-binding cassette (ABC) transport system and its corresponding regulatory protein (RbsR). Deletion of the structural genes rbsACBD prohibited ribose uptake. Deletion of the regulatory gene rbsR resulted in an increased mRNA level of the whole operon. Analysis of the promoter region of the rbs operon by electrophoretic mobility shift assays identified a catabolite-responsive element (cre)-like sequence as the RbsR-binding site. Additional RbsR-binding sites were identified in front of the recently characterized uriR operon (uriR-rbsK1-uriT-uriH) and the ribokinase gene rbsK2. In vitro, the repressor RbsR bound to its targets in the absence of an effector. A probable negative effector of RbsR in vivo is ribose 5-phosphate or a derivative thereof, since in a ribokinase (rbsK1 rbsK2) double mutant, no derepression of the rbs operon in the presence of ribose was observed. Analysis of the ribose stimulon in the C. glutamicum wild-type revealed transcriptional induction of the uriR and rbs operons as well as of the rbsK2 gene. The inconsistency between the existence of functional RbsR-binding sites upstream of the ribokinase genes, their transcriptional induction during growth on ribose, and the missing induction in the rbsR mutant suggested the involvement of a second transcriptional regulator. Simultaneous deletion of the regulatory genes rbsR and uriR finally demonstrated a transcriptional co-control of the rbs and uriR operons and the rbsK2 gene by both regulators, RbsR and UriR, which were furthermore shown to recognize the same cognate DNA sequences in the operators of their target genes.
- Published
- 2009
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